1. Field of Invention
The present invention relates to an improved method for uniformly spraying lubricants onto metal working surfaces such as dies in a forging press, rolls in a rolling mill stand or the like.
2. Brief Description of the Prior Art
Lubricants are applied to metal working surfaces, such as the dies in a heated forging press, for a number of reasons. A uniformly applied coating prevents forged metal from sticking to the dies, insures smooth surfaces on the forged article, reduces die wear and facilitates metal flow during the forging operation.
The most common method of applying lubricant to metal working surfaces is by pneumatic atomization. In this technique high velocity air is mixed with a lubricant prior to the air expansion through a nozzle toward the die or roll surface. Pneumatic atomization utilizes compressed air, approximately 30-100 psi, and produces a fine lubricant spray having drops in the 5-100 micron diameter range.
There are inherent disadvantages with the presently known pneumatic atomization techniques for lubricating metal working surfaces. First, the high velocity air coupled with the fine spray makes it difficult to accurately direct and uniformly apply the lubricant over the entire metal working surface, specially around corner radii and in web areas of intricately shaped dies in a forging press. Second, lubricants, particularly the more commonly used high viscosity lubricants, tend to clog the chambers, tubes and orifices of spraying nozzles. Third, the pneumatic technique inherently supplies a substantial quantity of air to the heated working surfaces where a portion of the lubricant is burned. Air increases the amount and rate of burned lubricant producing a large amount of smoke. This smoke can cause visual and respiratory problems for the workers in the area. Finally, it is time consuming and therefore costly to apply a uniform coat of lubricant when using a fine spray. An increase in spraying time decreases the number of articles that can be formed in a given period and is inefficient from an energy conservation viewpoint.
It has been disclosed in the prior art, such as Larsonneor U.S. Pat. No. 3,707,012 and Lyon et al U.S. Pat. No. 3,605,473, that lubricants for rolling mill applications may be mixed with large quantities, 50 to 99.999 percent of cooling water and the dispersion may be sprayed onto the work rolls under relatively high hydraulic and water pressure to provide an improved coolant and lubricant for the rolls. The oil/water dispersions disclosed in the prior art require mixing at much lower temperatures and application at much higher pressures than the heated lubricants of the present invention. Also, the dispersions disclosed in the prior art have an undesirable cooling effect when applied onto the surfaces of heated dies of a forging press, or the like.
Accordingly, a new method of applying lubricant to metal working surfaces is desired which eliminates the need for high velocity air, quickly applies a uniform coating over the entire working surface utilizing relatively low hydraulic pressure, and does not result in clogging of conventional spraying nozzles. This method prevents metal from sticking to metal working surfaces and increases the life of the dies or rolls.